Ringless piston



Feb. 6, 1934.

W. E. BASSETT ET AL RINGLESS PISTON Filed May 19, 1932 2 Sheets-Sheet l W m g L Baa-Jeff.

F ch. 6, 1934.

W. E. BASSETT ET AL RINGLESS PISTON Filed May 19, 1952 2 Sheets-Sheet 2 avwwwboz 1V- 5. fiasseif.

Patented Feb; 6, 1934 RHNGLIESS PIISTUN Willard 1E. Bassett and Bert IL. Bassett,

Detroit, Mich.

Application May 19, 1932. Serial No. 612,345 4i Claims. Cl. 309-111) This invention relates to pistons and has for an object to provide a piston devoid of the usual resilient piston rings order to eliminate such motor troubles as oil pumping, leaky rings, loss of compression, and piston slap.

A further object is to provide a piston having a solid head and a skirt step out along an axial plane to provide a pair of semi-cylindrical sections, one of which is integral with the head and the other of which is separate from the head, the sections being spring pressed apart to expand against the cylinder, the expansive tendency of the skirt being produced by opposite springs located on wrist pin bosses carried by the skirt sections, the location and arrangement of these springs producing uniform outward expansion of the skirt from about a central point on each skirt section.

A further object is to provide theskirt with integral ribs of the same outer diameter as the piston head to reduce friction of the piston, the sections of the ribs being lap jointed at the meeting edges of the skirt sections to promote a compression and oil tight fit.

A further object is to provide a sliding connection between the piston head and the separate skirt section, comprising a socket formed in the edge of the head and a lug formed on the inner face of the skirt section, to the end that the separate skirt section may be positively held against axial movement relative to the head but may easily slide radially outwardly under urge of the springs.

With the above and other objects in view the invention consists in certain novel details of construction and combinations of parts hereinafter fully described and claimed it being understood that various modifications may be resorted to within the scope of the appended claims without departing from the spirit or sacrificing any of the advantages of the invention.

in the accompanying drawings forming part of this specification,

Figure l is a side elevation of the pistondisposed in a cylinder shown in cross section.

Figure 2 is a longitudinal section through the piston assembled on the piston rod,

Figure 3 is a cross section taken on the line 3-3 of Figure 2,

Figure 4 is a longitudinal section through the solid piston head and one section of the skirt integral therewith,

Figure 5 is a longitudinal section of the mating section of the skirt, and

Figure 6 is a fragmentary side elevation showing the socket in the piston head.

Referring now to the drawings in which like characters of reference designatesimilar parts in the various views, 10 designates a cylinder, and 11 a piston rod having a bearing 12 which receives the wrist pin 13, these parts being all of the usual and well known construction.

The improved piston comprises a solid piston head 14 and a skirt formed of two sections 15 and 16 out along a plane passed through the longitudinal axis of the piston. The section 15 is cast integral with the head 14, while the section 16 is formed separate. Both sections of the skirt are step cut, that is, the section 15 is formed with notches 17 in each of its edges adapted to receive similarly shaped lugs 18 formed on the edges of the section 16.

Wrist pin bosses 19 and 20 are provided on the sections of the skirt and are preferably centered both with respect to the plane of separation of the sections and with respect to the solid head it and the open'bottom of the piston.

The piston head is provided with a thickened edge in the plane of the wrist pin bosses, which edge is undercut as shown at 21 and is also formed with a socket 22 above the undercut portion to receive a lug 23 which projects inwardly from the top edge of the separate skirt section 16 while the undercut portion 21 bears against the lower face of said lug. This interfitting connection between the piston head and separate section of the skirt prevents relative axial movement of the separate section with respect to the head while permitting free sliding movement in an outward direction under the urge of the hereinafter described springs to permit the skirt to expand tightly against the cylinder walls.

The head of the piston, it will be noted, is thickened or reinforced by means of a substantially cruciform integral projection 24, best shown in Figure 3. Two of the legs of this projection extend in the plane of the step out of the skirt sections while the other two legs extend in the plane of the boss 19 and boss 20 as shown. a

Mounted on the wrist pin bosses l9 and 20 are expansion springs 25 and 26, these springs being spiral in character and frusto-conical in shape to nicely surround the 'bosses and the wrist pin and bear with their inner ends against the bearing 12 of the piston rod and with their outer ends against the inner faces of the respective skirt sections. By means of these springs the two sections are continuously pressed away from each other toward the walls of the cylinder 10 to insure a gas tight fit.

To reduce friction on the walls of the cylinder the sections of the skirt are provided with integral arcuate rib sections 27 and 28 of the same radius as the head 14. The rib sections mate to form annular ribs encircling the skirt when the skirt sections are assembled, corresponding to the compression and oil rings of ordinary pistons. The step cuts of the skirt secof the rib sections so that each annular rib is lap jointed at diametrically opposite points, as "shown at 29 in Figure 1, to further insure a gas and oil tight fit.

From the above description it will be noted piston rings of conventional form are obviated and that the piston is formed essentially of but two separate parts, the unitary head and skirt section being one part, and the separate skirt section being the other part. Also it will be noted that the sections of the skirt are confined rigidly against relative axial movement while being permitted to freely expand radially under the urge of the opposed springs which surround the wrist pin.

From the above description it is thought that the construction and advantages of the invention will be fully understood without further explanation.

What is claimed is: l. A piston comprising a head having a sub- I stantially cruciform reinforcement on the inner face, said reinforcement having pairs of legs, a skirt comprising sections separated along a plane passing through the longitudinal axis of the piston and through a pair of the legs of said reinforcement, one of said sections being integral with said head,. a sliding connection between the other of said sections and said head disposed in the plane of another pair of the legs of the cruciform reinforcement, wrist pin bosses on the sections of the skirt, and expansion springs seated on said bosses and normally urging said sections laterally apart.

2. A piston comprising a head and a skirt, said skirt being divided into two parts separated along a plane passing through the longitudinal axis of the piston, one of said sections being integral with the head and the other of said sections having a sliding connection with said head at the top edge of the section, integral rib sections on the sections of the skirt of arcuate shape coacting in producing annular ribs when the skirt sections are assembled, there being step joints formed in the skirt sections at the meeting ends of the arcuate rib sections to produce gas and oil tight joints, said ribs and said head of the piston being of indentical radius and being adapted to engage the walls of the cylinder, and means between the sections for urging the sections radially apart.

3. A piston including a head, a skirt divided longitudinally to produce opposite sections, one of said sections being integral with the head, interfitting means between the head and the other said section securing said other section against axial movement relative to the head but permitting radial movement relatively to the head, said skirt sections interfitting at their -long'itu-' dinal confronting edges, integral rib sections formed on the skirt sections and interfitting at their meeting edges to produce lap jointed annular ribs, and springs between the sections exerting radial pressure against the sections to move the same outwardly.

4. A piston comprising a head thickened to provide a reinforcement projecting from the inner face of the head, a skirt comprising sections separated along a plane passing through the iongitudinal axis of the piston at a right angle to said reinforcement, one of said sections being integral with the head and saidreinforcement being undercut at one end and recessed to provide a socket, a lug carried by the other section at the top edge and fitting in said socket, said undercut engaging the inner face of the latter skirt section below said lug, and means urging the skirt sections laterally apart.

WILLARD E. BASSETT. BERT L. BASSETI. 

